CN108148210B

CN108148210B - Intramolecular cross-linked polymer, preparation method and application thereof

Info

Publication number: CN108148210B
Application number: CN201810036754.0A
Authority: CN
Inventors: 侯铮迟; 陆闰三; 杨海军; 梁坤坤; 杨宁
Original assignee: Shanghai Institute of Applied Physics of CAS; University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2018-01-15
Filing date: 2018-01-15
Publication date: 2020-11-27
Anticipated expiration: 2038-01-15
Also published as: CN108148210A

Abstract

The invention discloses an intramolecular cross-linked polymer, a preparation method and application thereof. The invention provides a preparation method of an intramolecular cross-linked polymer, which comprises the following steps: in a polar organic solution, under the irradiation of gamma rays, carrying out intramolecular crosslinking reaction on a polymer; the ratio of the degradation radiochemical yield to the crosslinking radiochemical yield of the polymer is less than 1.00; the polymer forms a homogeneous solution with the polar organic solution. The invention also provides an intramolecular cross-linked polymer obtained by the preparation method, which has the characteristics of low viscosity and large surface area, can be used as an additive of a coating and an adhesive, a filler and a pigment of a reinforcing material, a carrier of medical and biological materials and the like, and has wide application.

Description

Intramolecular cross-linked polymer, preparation method and application thereof

Technical Field

The invention relates to an intramolecular cross-linked polymer, a preparation method and application thereof.

Background

Polyvinylidene fluoride (PVDF) is a functional material with excellent properties developed in the 70 s of the 20 th century. PVDF has outstanding stiffness, hardness, creep resistance, has the advantages of smaller relative density, lower melting point, good melt flowability, etc., and is the least expensive of all fluoropolymers, as calculated by the price of the polymer per unit volume. To date, PVDF is a fluoropolymer in commercial quantities second only to Polytetrafluoroethylene (PTFE). Meanwhile, PVDF is also a common radiation crosslinking polymer.

When a polymer material is subjected to high-energy ionizing radiation, including gamma rays, electron beams, X rays and the like, a series of reactions such as ionization, excitation and the like occur to generate various chemical and physical changes. When most polymers are irradiated, crosslinking and degradation occur simultaneously, but a major and minor component. PVDF is often irradiated in the solid phase or under heterogeneous conditions to form intermolecular cross-linked polymers. The preparation research of the PVDF intramolecular cross-linked macromolecule is not reported before.

The intramolecular cross-linked macromolecule has a cross-linked structure and is soluble, so that the performance of a cross-linked polymer can be conveniently researched, and the performance such as density, viscosity and the like which cannot be researched by a plurality of intermolecular cross-linked macromolecules can be researched. Furthermore, the intramolecular cross-linked macromolecules have low viscosity and large surface area, and can be used as additives of coatings and adhesives, fillers of reinforcing materials and pigments, carriers of medical and biological materials and the like in industrial production, and have wide application.

The polymer receives ionizing radiation energy, including gamma rays, electron beams or X rays, and generates active substances such as free radicals, thereby initiating a radiation effect. With radiation crosslinking being the most widely used radiation effect. Due to the above chemical changes, changes in the physical properties of the polymer are often caused, such as solubility, melting point, electrical properties, mechanical properties, etc.

However, the cross-linking generally defined in the art means that a specific technical means is used to form chemical bonds or around strong physical bonding points between long polymer chains of the polymer, so that the physical and chemical properties of the polymer are improved and new properties are possibly introduced. The existing radiation crosslinking refers to a technical means for initiating a crosslinking reaction between polymer long chains by using various kinds of radiation.

In the prior art, the methods commonly used for preparing intramolecular cross-linked polymers such as polyvinyl alcohol (PVA, molecular weight of about 30000), polyoxytetramethylene glycol (PTMG, molecular weight of 900-. However, the polymerization reaction often has a complicated preparation process, requires a large amount of raw materials, also requires heating and post-treatment processes, requires at least reaction monomers, solvents, crosslinking agents, initiators, and possibly chain extenders, terminators, and catalysts, is a reaction which is difficult to control, and requires repeated heating and cooling in the reaction process, which is very complicated. And the product is difficult to separate. Only laboratory research can be carried out, and the method has scientific significance and hardly has industrial application value; and the prepared molecular weight is still small, and the performance is still insufficient, which restricts the industrial application of the intramolecular cross-linked polymer, so that a new and better method for preparing the intramolecular cross-linked polymer, particularly a macromolecular polymer, is urgently needed.

Disclosure of Invention

The invention aims to solve the technical problems that the existing preparation method for chemically synthesizing the intramolecular cross-linked polymer has complicated flows, needs a large amount of raw materials, needs heating and post-treatment processes, and has the defects that the reaction process of cross-linking polymerization is difficult to control and the like, and provides the intramolecular cross-linked polymer, the preparation method and the application thereof. The method is simple to operate and easy to control, and the prepared polyvinylidene fluoride intramolecular cross-linked polymer has the characteristics of low viscosity and large surface area, can be used as an additive of a coating and an adhesive, a filler and a pigment of a reinforcing material, a carrier of medical and biological materials and the like, and has wide application.

The invention provides a preparation method of an intramolecular cross-linked polymer, which comprises the following steps: in a polar organic solution, under the irradiation of gamma rays, carrying out intramolecular crosslinking reaction on a polymer; the ratio of degradation radiochemical yield (G (X)) to crosslinking radiochemical yield (G (S)) of the polymer is less than 1.00; the polymer forms a homogeneous solution with the polar organic solution.

The radiochemical yield, denoted by G, is defined as the number of molecules that change per 100eV of energy absorbed, G ═ molecule/100 eV. For example, the crosslinking radiochemical yield (or radiochemical yield of radiation crosslinking, G (X)) is the number of molecules that undergo a crosslinking change per 100eV of energy absorbed; the degradation radiochemical yield (or radiolysis chemical yield, g (s)) is the number of molecules that undergo a degradation change per 100eV of energy absorbed. The radiochemical yield is determined as conventional in the art, at room temperature (25 c 5 c), in the absence of oxygen,⁶⁰co source irradiation lower testAnd (5) obtaining the product. (reference may be made to the following written and literature: [1 ]]Tabata,Y.,Ito,Y.,Tagawa,S.,eds.CRC Handbook of Radiation Chemistry.CRC Press,Boca Raton,FL,1991.[2]Dawes,K.,Glover,L.Effects of electron beam and γ-irradiation on polymer materials.In Mark,J.,ed.Physical Properties of Polymers Handbook.AIP Press,American Institute of Physics,Woodbury,1996,chap.41.)

Wherein the polar organic solvent may be a polar organic solvent conventional in the art, such as one or more of N-methylpyrrolidone (NMP), N-Dimethylacetamide (DMAC) and Dimethylsulfoxide (DMSO), which can dissolve the polymer.

The polymer may be a polymer conventional in the art, such as polyethylene, polystyrene, polyvinyl fluoride, polybutadiene, polyvinyl acetate, polyacrylamide, polytrifluoroethylene (PTrFE), poly (ethylene-tetrafluoroethylene) (ETFE), polyvinylidene fluoride (PVDF), poly (ethylene-chlorotrifluoroethylene) (ECTFE), poly (tetrafluoroethylene-propylene) (TFEP), poly (vinylidene fluoride-tetrafluoroethylene) (VDF-TFE), poly (vinylidene fluoride-chlorotrifluoroethylene) (VDF-CTFE), poly (vinylidene fluoride-hexafluoropropylene) (VDF-HFP), or natural rubber; for example, polyvinylidene fluoride having a weight average molecular weight of 670000 to 700000 (e.g., 6020 type polyvinylidene fluoride available from Soerve)

The polymer may be in a form conventional in the art, such as a powder or fiber, and further such as a powder.

The mass percentage of the polymer in the homogeneous solution may be conventional in the art so as not to affect the reaction (e.g., 8-15%; e.g., 10-12%).

In the present invention, the radiation source for the intramolecular crosslinking reaction may be a gamma ray radiation source (for example, gamma ray radiation source) which is conventional in the art⁶⁰Co)。

The total dose of radiation for the intramolecular cross-linking reaction may be a dose conventional in the art, for example not exceeding the critical dose value required for the polymer to undergo detectable damage or severe damage under the action of ionizing radiation, again for example 18 to 64KGy (also for example 30 KGy).

The average dosage rate of the intramolecular crosslinking reaction is the average dosage rate conventional in the field (for example, 1-5.00 kGy/h, and for example, 1.67-3.56 kGy/h).

The temperature of the intramolecular cross-linking reaction may be a temperature conventional in the art for such reactions (e.g., 20-30 ℃, e.g., 25 ℃).

The atmosphere for the intramolecular cross-linking reaction may be an atmosphere conventional in the art, for example, an oxygen-free atmosphere. The oxygen-free atmosphere is, for example, nitrogen or argon.

The oxygen-free atmosphere can be obtained by means of a technique conventional in the art, such as introducing nitrogen and/or argon into the reaction system before irradiation to remove oxygen from the system.

The preparation method is preferably carried out before the irradiation of the polymer, and the pretreatment operation which is conventional in the field can be carried out. The pretreatment operation is carried out before the homogeneous irradiation crosslinking reaction, so that impurities which influence the irradiation crosslinking reaction in the raw materials can be removed as much as possible.

The pretreatment operation may be conventional in the art and includes the following steps: washing and soaking the raw materials, and drying the raw materials in vacuum to constant weight; preferably comprising the steps of: washing the raw materials with deionized water, soaking in deionized water for more than one week, replacing deionized water for multiple times, and vacuum drying to constant weight.

In the pretreatment operation, the operation and conditions of the vacuum drying may be those conventional in the art, such as operation in a vacuum drying oven; the temperature of the vacuum drying is, for example, 60-80 ℃; the vacuum degree of vacuum drying is, for example, 0.06-0.08 MPa.

The preparation method preferably further comprises the step of carrying out post-treatment operation on the homogeneous solution obtained after the crosslinking. The work-up operation may be conventional in the art and comprises the following steps: and (3) performing reverse-phase precipitation on the homogeneous solution obtained after the crosslinking reaction in deionized water, washing the obtained solid for a plurality of times, soaking the solid in the deionized water, and then performing vacuum drying to constant weight.

In the post-treatment operation, the soaking time may be conventional in the art, and is preferably 20 to 26 hours (h). The vacuum drying operations and conditions may be those conventional in the art, for example, in a vacuum drying oven. The temperature of the vacuum drying is, for example, 40-60 ℃; the vacuum degree of the vacuum drying is, for example, 0.06-0.08 MPa.

The invention provides an intramolecular cross-linked polymer, which is prepared by the preparation method; in the preparation method, the polymer is preferably polyvinylidene fluoride (such as polyvinylidene fluoride with the weight-average molecular weight of 670000-700000; such as polyvinylidene fluoride with the model number of 6020 of Solvay).

The invention also provides a polyvinylidene fluoride intramolecular cross-linked polymer, which has a rotational viscosity value of 1.17-1.23 mpa-s (millipascal seconds), a mean square rotational radius of 7.98-9.15 nm, a fractal dimension value of 1.55-1.84, an intrinsic viscosity value of 0.151-0.208L/g and a weight-average molecular weight of 770000-870000.

The invention also provides the application of the polyvinylidene fluoride intramolecular cross-linked polymer as an additive in a pigment or a coating.

The above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.

The reagents and starting materials used in the present invention are commercially available unless otherwise specified.

The positive progress effects of the invention are as follows: (1) compared with the traditional chemical preparation of intramolecular cross-linking solution polymerization and emulsion polymerization methods, the preparation method of the intramolecular cross-linking polymer has many advantages, namely 1. the raw materials only need polymer and solvent, and no monomers, initiators, emulsifiers, terminators and other raw materials are needed, the post-treatment is relatively simple, and relatively pure intramolecular cross-linking polymer can be obtained; 2. the gamma ray has strong penetrating power, forms free radicals uniformly in the whole system to carry out intramolecular crosslinking reaction, has simple operation, and can be carried out under the condition of normal temperature without heating reaction; 3. the crosslinked product can be controlled by adjusting the radiation dose, the polymer concentration, and the like. (2) The prepared intramolecular cross-linked polymer, such as polyvinylidene fluoride intramolecular cross-linked polymer, has the characteristics of low viscosity and large surface area, can be used as an additive of a coating and an adhesive, a filler and a pigment of a reinforcing material, a carrier of medical and biological materials and the like, and has wide application.

Drawings

FIG. 1 is a TGA graph of samples of examples 1-3 and comparative example 1.

FIG. 2 is a DSC chart of samples of examples 1 to 3 and comparative example 1.

Figure 3 is a fitted GPC standard curve.

FIG. 4 is a GPC outflow time curve for samples of examples 1-3 and comparative example 1.

FIG. 5 is lnI-q of samples of examples 1 to 3 and comparative example 1²Function graph, where q is the scattering vector and I is the scattering intensity.

FIG. 6 is a plot of lnI-lnq as a function of time for the samples of examples 1-3 and comparative example 1.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

In the following examples and comparative examples, the polyvinylidene fluoride (PVDF) in examples 1-3 and comparative example 1 was 6020, available from Solvay group, and had a weight average molecular weight of 67 ten thousand, and both were subjected to the following pretreatment operations before being subjected to the irradiation reaction: washing raw material polyvinylidene fluoride with deionized water, soaking in the deionized water for more than one week, replacing the deionized water for many times, and vacuum drying (70 deg.C, vacuum degree 0.07MPa) the raw material polyvinylidene fluoride with a vacuum drying oven to constant weight.

Example 1

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

After the irradiation reaction is finished, the obtained homogeneous solution is subjected to post-treatment operation according to the following steps: and (3) performing reverse-phase precipitation on the homogeneous solution in deionized water, washing the obtained white solid for a plurality of times, soaking the white solid in the deionized water for 24 hours, pouring the deionized water, and performing vacuum drying (50 ℃, the vacuum degree of 0.07MPa) on the obtained solid in a vacuum oven to constant weight to obtain the sample.

Example 2

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of DMAC solvent, stirring for 24 hours to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

Example 3

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of DMSO solvent, stirring for 24 hours to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

Example 4

Accurately weighing 20g of pretreated PVDF powder, dissolving in 230g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰Carrying out radiation reaction at 25 deg.C under CO source at dose rate of 3.56kGy/h, and absorbingThe dose was 64 kGy.

Example 5

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 180g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

Example 6

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 120g of NMP solvent, stirring for 24 hours to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

Example 7

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰Under a CO source, in 2The radiation reaction is carried out at the temperature of 5 ℃, the dosage rate is 1kGy/h, and the absorbed dose is 64 kGy.

Example 8

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 1.67kGy/h, and the absorbed dose is 64 kGy.

Example 9

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰And carrying out radiation reaction at 25 ℃ under a CO source, wherein the dose rate is 5kGy/h, and the absorbed dose is 64 kGy.

Example 10

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂After the reaction lasts for more than 25min,placing the homogeneous solution in⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 18 kGy.

Example 11

Accurately weighing 20g of pretreated PVDF powder, dissolving the PVDF powder in 150g of NMP solvent, stirring for 24h to obtain a homogeneous solution, introducing N₂Standing for more than 25min, and standing the homogeneous solution⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 30 kGy.

Comparative example 1

The PVDF powder is pretreated as above.

Comparative example 2

Accurately weighing 20g of pretreated PVDF powder, and placing in N₂In the atmosphere, placing in⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

After the irradiation reaction is finished, washing the obtained white solid for a plurality of times, soaking the white solid in deionized water for 24h, pouring the deionized water, and drying the obtained solid in a vacuum oven in vacuum (50 ℃, the vacuum degree of 0.07MPa) to constant weight to obtain a sample.

Comparative example 3

Accurately weighing 20g of pretreated PVDF powder, dissolving in 150g of deionized water, introducing N₂After a duration of more than 25min, the heterogeneous solution is placed in⁶⁰The radiation reaction is carried out at 25 ℃ under a CO source, the dosage rate is 3.56kGy/h, and the absorbed dose is 64 kGy.

Effect example 1

The samples obtained in examples 1 to 3 and comparative example 1 were subjected to thermogravimetric Analysis (TG or TGA) test, and the results are shown in FIG. 1.

TGA test: in this experiment, samples of examples 1 to 3 and comparative example 1 were tested on a TG 209F3Tarsus thermogravimetric analyzer (NETZSCH, Germany) in a nitrogen atmosphere at an airflow rate of 20mL/min, a heating rate of 10 ℃/min and a heating temperature in the range of 30-800 ℃. The change in decomposition temperature of polyvinylidene fluoride before and after homogeneous irradiation will be studied.

FIG. 1 is a TGA plot of samples of examples 1-3 and comparative example 1. As can be seen from FIG. 1, the thermal weight loss curve of polyvinylidene fluoride after homogeneous irradiation is obviously shifted to the high temperature side, and the decomposition temperature is increased, which proves that the irradiation of PVDF in a homogeneous system can initiate the crosslinking reaction.

Effect example 2

The products obtained in examples 1 to 3 and comparative example 1 were subjected to Differential Scanning Calorimetry (DSC) test, and the results are shown in fig. 2.

DSC test: in this experiment, samples of examples 1 to 3 and comparative example 1 were tested on a NETZSH DSC200 differential scanning calorimeter (NETZSCH, Germany). The testing parameters are 25-250-25 ℃, the heating rate is 10 ℃/min, and the nitrogen flow rate is 60 mL/min. In order to eliminate the thermal history of the powder, the same scanning parameters are scanned twice, and the experimental result is the result of the second scanning. The change in melting point of polyvinylidene fluoride before and after homogeneous irradiation will be investigated.

FIG. 2 is a DSC chart of samples of examples 1 to 3 and comparative example 1. As can be seen from FIG. 2, the melting point of polyvinylidene fluoride is increased significantly after homogeneous irradiation, which proves that irradiation of PVDF in a homogeneous system can initiate crosslinking reaction.

Effect example 3

The products obtained in examples 1 to 11 and comparative examples 1 to 3 were subjected to Gel Permeation Chromatography (GPC) test.

Standard curve: prepared from a narrow-distribution polystyrene standard series supplied by the instrument manufacturer TOSOH corporation of japan. Respectively using a weight average molecular weight of 2.11X 10⁶、1.09×10⁶、7.06×10⁵、4.27×10⁵GPC elution times of polystyrene standard samples (labeled as Standard samples 1 to 4) were determined, and GPC standard curves were obtained by polynomial fitting, y being 1.24697E8-3.84514E7x +2.97492E6x²Where x is the time of efflux, y is the weight average molecular weight value, and E8, E7, E6 are the powers of 8, 7 and 6 of 10, respectively. According to this formula, a specific weight average molecular weight value can be obtained. Figure 3 is a fitted GPC standard curve.

TABLE 1 Standard 1-4 samples specific run-off time and weight average molecular weight

Sample (I)	Size of molecular weight	Outflow time/(s)
			Standard sample 1	2.11×10⁶	5.72
Standard sample 2	1.09×10⁶	5.975
			Standard sample 3	7.06×10⁵	6.21
Standard sample 4	4.27×10⁵	6.455

GPC measurement: in the experiment, samples of examples 1 to 11 and comparative example 1 were tested by an HLC-8220 type gel permeation chromatograph (TOSOH, Japan), and before the test, a sample to be tested was first dissolved in a DMF solution containing 30mmol/L LiBr to prepare a sample solution of 4mg/mL, the sample solution was put into a vial by a small filtration device, and the vial was placed in a GPC sample cell, and then the test was carried out, wherein the types of chromatographic columns were AW3000 and AW5000, the column temperature was 40 ℃, and the flow rate was 0.6 mL/min. The change of the flow-out time of the polyvinylidene fluoride before and after the homogeneous irradiation was investigated.

TABLE 2 specific run-out times for the samples of examples 1 to 11 and comparative examples 1 to 3

FIG. 4 is a GPC outflow time curve of samples of examples 1 to 3 and comparative example 1, and Table 2 shows specific values of the outflow time and weight average molecular weight of samples of examples 1 to 11 and comparative examples 1 to 3.

In the high molecular irradiation effect, degradation is a decrease in molecular weight, intramolecular cross-linking is a constant molecular weight, and intermolecular cross-linking is an increase in molecular weight, so it is inferred from GPC experiments and from changes in molecular weight that the irradiation reaction is mainly intramolecular or intermolecular cross-linking or degradation.

As can be seen from FIG. 4, the elution time of GPC after irradiation of the polyvinylidene fluoride of comparative examples 2 and 3 in the solid phase and the heterogeneous phase was greatly reduced as compared with comparative example 1 (no irradiation). Preliminary judgment shows that the polyvinylidene fluoride forms intermolecular crosslinking, so that the molecular weight of the polymer is increased, and the outflow time is shortened.

As can be seen from fig. 4, the polyvinylidene fluoride of examples 1-3 is significantly different from comparative examples 2 and 3 after being subjected to homogeneous irradiation, and the flowing-out time is only slightly reduced compared with comparative example 1. The primary judgment is that due to the formation of intramolecular cross-linking, the structure of PVDF after uniform irradiation is changed from the trend linear structure before non-irradiation to the trend spherical structure after irradiation, the size of the PVDF polymer chain is increased in a certain dimension, and the outflow time is reduced due to the volume exclusion theory.

Thus, homogeneous radiation products are dominated by intramolecular cross-linking, while heterogeneous radiation products are dominated by intermolecular cross-linking.

In addition, as can be seen from table 2, in examples 1 to 11, the concentration, the irradiation dose rate, the irradiation dose and other factors are within the above ranges, and the influence on the formation of the intramolecular cross-linking product of polyvinylidene fluoride in the homogeneous system is not very obvious. Specifically, the polyvinylidene fluoride concentration, the irradiation dose rate and the irradiation dose increase and then decrease.

Effect example 4

The rotational viscosity test was carried out on the products obtained in examples 1 to 3 and comparative examples 1 to 3, and the results are shown in Table 3.

Rotational viscosity test: in this experiment, the samples of examples 1 to 3 and comparative example 1 were tested on an NDJ-79 type rotational viscometer (Shanghai Changji Co., Ltd.). Before testing, a sample to be tested is dissolved in a DMF solution to prepare a 1g/L organic solution, and then the test is carried out. The sample solution to be measured is placed in a constant temperature water bath kettle at 25 ℃, the temperature of the controller is constant at 25 ℃, and meanwhile, the room temperature is controlled at 25 ℃. And selecting a third unit rotor and testing under the condition of 750 revolutions per minute. The rotational viscosity change of polyvinylidene fluoride before and after homogeneous irradiation will be studied.

TABLE 3 rotational viscosity values for the samples of examples 1-3 and comparative example 1

Sample (I)	Rotational viscosity/(mpa · s)
		Example 1	1.23
Example 2	1.20
		Example 3	1.17
Comparative example 1	1.36
		Comparative example 2	1.57
Comparative example 3	1.56

Table 3 shows the values of rotational viscosity for the samples of examples 1 to 3 and comparative example 1. As can be seen from Table 3, the viscosity of the homogeneous organic solution of PVDF decreases after homogeneous irradiation. The viscosity of the polymer solution is reduced for two common reasons, one is that polyvinylidene fluoride undergoes degradation reaction after being irradiated in homogeneous phase, but the explanation is not consistent with the above experiments of TGA and DSC, and is not consistent with the theory that PVDF is known to be a radiation crosslinking polymer, and is difficult to be established. Another explanation is that the PVDF structure changes after uniform irradiation due to intramolecular cross-linking, and the PVDF random coil in the solution shrinks as a whole, and becomes smaller in overall size and more dense, so that the interaction with the dispersion medium decreases, and the viscosity of the solution system decreases.

It was thus demonstrated by GPC measurements and rotational viscosity measurements that irradiation of PVDF in a homogeneous system gives a product which is an intramolecular crosslinked polymer of PVDF.

After PVDF is irradiated in a solid phase and a heterogeneous phase by polyvinylidene fluoride, the viscosity of a homogeneous organic solution of the PVDF can be obviously increased. It can be judged that the polyvinylidene fluoride may form intermolecular cross-linking, which increases the viscosity of the homogeneous organic solution.

It was thus demonstrated by GPC measurements and rotational viscosity measurements that irradiation of PVDF in the solid phase and in the heterogeneous phase gave products which were intermolecular crosslinked polymers of PVDF.

Effect example 5

The intrinsic viscosity test was performed on the products obtained in examples 1 to 3 and comparative example 1, and the results are shown in Table 4.

Intrinsic viscosity test: the test was carried out on samples of examples 1 to 3 and comparative example 1 using a fully automatic Ubbelohde viscometer (SI analytical CT72/2, Germany). Before the test is started, the test solution is prepared according to the concentration of 0.5g/L, N-dimethylformamide DMF is taken as a solvent, and after the solution is fully dissolved, the volume is determined in a volumetric flask. After the mixture is placed for 24 hours after the volume is fixed, the macromolecule is fully stretched in the solvent and then diluted by DMF to the original concentration of 1/2, 1/4, 1/8 and 1/16 by four gradients. During measurement, the polymer solution is added into the viscometer, the solution is sucked to the position above the scales, the time required for the solution to flow through the two scale lines is recorded, the process is repeated for 3 times, the data error does not exceed 5% every time, and the average value is taken. After the test is completed with one concentration of solution, the solution is poured off, washed with the original solvent, rinsed with the next concentration of solution, and then the next concentration of solution to be tested is added, and the operation is carried out, so that data are obtained. The flow-out time of the 5-concentration solution was plotted on the ordinate and the concentration on the abscissa, and 5 points were recorded. And fitting 5 data points to obtain a curve, wherein the intercept of the curve is the intrinsic viscosity corresponding to the macromolecule. The change in intrinsic viscosity of polyvinylidene fluoride before and after homogeneous irradiation will be investigated.

TABLE 4 intrinsic viscosity values for the samples of examples 1-3 and comparative example 1

Table 4 shows the intrinsic viscosity values of the samples of examples 1 to 3 and comparative example 1. As can be seen from Table 4, the intrinsic viscosity of the homogeneous organic solution of PVDF decreases after homogeneous irradiation. This is consistent with the trend of the properties of the rotational viscosity. After uniform irradiation, the structure of PVDF is changed, the PVDF random coil in the solution can shrink on the whole, the whole size becomes small, and therefore, the interaction between the PVDF random coil and a dispersion medium can be reduced, and the viscosity of the solution system becomes small.

Rotational viscosity and intrinsic viscosity tests therefore demonstrate that irradiation of PVDF in a homogeneous system results in a product that is an intramolecular cross-linked polymer of PVDF.

Effect example 6

The products obtained in examples 1 to 3 and comparative example 1 were subjected to X-ray small angle scattering test, and the results are shown in FIGS. 5 to 6 and Table 5.

X-ray small angle scattering test: the experiment is carried out on a Shanghai synchrotron radiation light source X-ray small-angle scattering experiment station (BL16B 1). The line station adopts a bent iron light source, and the energy resolution is 6 multiplied by 10^-4The energy range is 5-20 keV, and the incident X-ray wavelength is 0.124 nm. The distance from the SAXS sample to the detector is 5050mm, the sample is placed on a three-dimensional sample table, the sample is irradiated by using focused monochromatic light, a Mar165CCD detector is used for detecting a small-angle scattering signal, and data are subjected to normalization processing by using fit2d software.

Changes of mean square rotation radius and fractal dimension of polyvinylidene fluoride before and after homogeneous irradiation are researched.

FIG. 5 is lnI-q of samples of examples 1 to 3 and comparative example 1²Function graph, where q is the scattering vector and I is the scattering intensity. From FIG. 4 and Guinier's theorem

The mean square radius of rotation R can be obtained_g ²Average size information of the whole of the reaction sample.

FIG. 6 is a plot of lnI-lnq function of samples of examples 1-3 and comparative example 1, and fractal dimension information of the samples can be obtained. The X-ray small angle scattering curve can be generally divided into Guinier region, Fractal region and Porod region, wherein

(R is the correlation length, R)₀Is the radius of the scattering element) as a fractal region. In this region: the fractal dimension can be found from α, which is the slope of the lnI (q) versus lnq curve. When 0 is present<α<When 3, the scatterer belongs to mass fractal, and the fractal dimension D is alpha, at the moment, the inside of the particle is loose, and the larger D is, the denser the inside of the system is; when 3 is<α<At 4, the scatterer is of surface fractal, the fractal dimension D is 6-alpha, at this time, the inside of the particle is dense, and the larger D is, the smoother the surface of the particle is. Therefore, a fractal dimension D value can be obtained, and the compactness degree of the interior of the reaction sample can be obtained.

TABLE 5 mean square radius of rotation and fractal dimension values for samples of examples 1 to 3 and comparative example 1

Sample (I)	Mean square radius of rotation/nm	Fractal dimension
			Comparative example 1	9.48	1.41
Example 1	8.91	1.59
			Example 2	9.15	1.55
Example 3	7.98	1.84

Table 5 shows the mean square radius of rotation and fractal dimension values for the samples of examples 1 to 3 and comparative example 1. As can be seen from Table 5, after the PVDF is subjected to homogeneous irradiation, the mean square radius of rotation is reduced, the fractal dimension is increased, and the overall average size is reduced, so that the sample becomes more compact.

Therefore, X-ray small-angle scattering experiments also prove that the product obtained by irradiating the PVDF in a homogeneous system is an intramolecular cross-linked polymer of the PVDF.

Effect example 7

100g of aqueous fluorine paint (purchased from national chemical agents Co., Ltd.) was weighed, 1g of each of examples 1 to 3 was added, the mixture was mixed and stirred uniformly for 30min, the paint was spread uniformly on a glass plate to form a film, the film was dried for 24h, and the film was weighed. The coating film was immersed in water at 20 ℃ and 5 ℃ for 24 hours, taken out and immediately dried by filter paper, and weighed again to calculate the weight increase percentage, i.e., water absorption. The calculation formula is as follows:

in the formula: m1 is the original mass of the coating film, and m2 is the mass of the coating film after soaking. The larger the water absorption, the poorer the water resistance of the coating film. The comparative example was a waterborne fluorine coating at this time. The change in water resistance of the aqueous fluorine paint after the addition of the prepared additive was investigated.

TABLE 6 Water absorption of samples of examples 1 to 3 and comparative example 1

Table 6 shows the water absorption of the coating films of the samples of examples 1 to 3 and comparative example 1. As can be seen from Table 6, the addition of examples 1-3 to the aqueous fluorine coating greatly reduced the water absorption of the coating, improved the water resistance, and improved the performance of the coating.

In fact, owing to the particular properties and advantages of the intramolecularly crosslinked polymers, their use in pigments and paints, whether aqueous or non-aqueous, improves their sagging properties, increases their film-forming properties, increases their tensile strength, lowers their viscosity, adjusts their rheological properties, increases their abrasion resistance, increases their crack resistance, increases their leveling properties, increases their wrinkle resistance and, in the appropriate circumstances, increases their water permeability.

Claims

1. A method for preparing an intramolecular cross-linked polymer, comprising the steps of: in a polar organic solution, under the irradiation of gamma rays, carrying out intramolecular crosslinking reaction on a polymer; the ratio of the degradation radiochemical yield to the crosslinking radiochemical yield of the polymer is less than 1.00; the polymer is polyvinylidene fluoride; the total radiation dose of the intramolecular cross-linking reaction is 18-64 KGy; the temperature of the intramolecular cross-linking reaction is 20-30 ℃; the average dosage rate of the intramolecular crosslinking reaction is 1-5.00 kGy/h; the atmosphere of the intramolecular cross-linking reaction is an oxygen-free atmosphere; the polymer is polyvinylidene fluoride with the weight-average molecular weight of 670000-700000; the polymer forms a homogeneous solution with the polar organic solution.

2. The method according to claim 1, wherein the polar organic solvent is one or more of N-methylpyrrolidone, N-dimethylacetamide, and dimethylsulfoxide;

and/or the polymer is in the form of powder or fiber;

and/or the polymer accounts for 8-15% of the homogeneous solution by mass;

and/or the radiation source of the intramolecular cross-linking reaction is⁶⁰Co。

3. The preparation method according to claim 2, wherein the polymer accounts for 10-12% by mass of the homogeneous solution;

and/or the total radiation dose of the intramolecular cross-linking reaction is 30-64 KGy;

and/or the average dosage rate of the intramolecular crosslinking reaction is 1.67-3.56 kGy/h;

and/or the temperature of the intramolecular cross-linking reaction is 25 ℃;

and/or the atmosphere of the intramolecular cross-linking reaction is nitrogen or argon.

4. A production process according to any one of claims 1 to 3, wherein the polymer is further subjected to a pretreatment operation before the irradiation;

and/or the preparation method also comprises the step of carrying out post-treatment operation on the homogeneous solution obtained after the crosslinking.

5. The method of claim 4, wherein the pre-treating step comprises the steps of: washing and soaking the raw materials, and drying the raw materials in vacuum to constant weight;

and/or, the post-processing operation comprises the following steps: and (3) performing reverse-phase precipitation on the homogeneous solution obtained after the crosslinking reaction in deionized water, washing the obtained solid for a plurality of times, soaking the solid in the deionized water, and then performing vacuum drying to constant weight.

6. The method of claim 5, wherein the pre-treating operation comprises the steps of: washing the raw materials with deionized water, soaking in deionized water for more than one week, replacing deionized water for multiple times, and vacuum drying to constant weight;

and/or, in the pretreatment operation, the vacuum drying is carried out in a vacuum drying box;

and/or in the pretreatment operation, the temperature of the vacuum drying is 60-80 ℃;

and/or in the pretreatment operation, the vacuum drying vacuum degree is 0.06-0.08 MPa;

and/or, in the post-treatment operation, the soaking time is 20-26 hours;

and/or, in the post-treatment operation, the vacuum drying is carried out in a vacuum drying oven;

and/or in the post-treatment operation, the temperature of the vacuum drying is 40-60 ℃;

and/or in the post-treatment operation, the vacuum degree of the vacuum drying is 0.06-0.08 MPa.

7. A polyvinylidene fluoride intramolecular cross-linked polymer produced by the production method according to any one of claims 1 to 6.

8. The polyvinylidene fluoride intramolecularly crosslinked polymer of claim 7, wherein the rotational viscosity value is 1.17 to 1.23 mpa-s, the mean square radius of rotation is 7.98 to 9.15nm, the fractal dimension value is 1.55 to 1.84, the intrinsic viscosity value is 0.151 to 0.208L/g, and the weight average molecular weight is 770000 to 870000.

9. Use of the polyvinylidene fluoride intramolecularly crosslinked polymer of claim 8 as an additive in a pigment or coating.